Enum DaemonTarget 

pub enum DaemonTarget<'a> {
    Skip,
    Client(&'a ControlClient),
    Unavailable(String),
}

What the fourth check has to work with.

Unavailable exists so a daemon that will not start is still reported as a daemon failure rather than aborting the command: the caller auto-starts one before the checks begin, and if that abort propagated, lev doctor would refuse to tell you whether your credentials were fine - which is most of what it is for.

Variants

Skip

Do not run the fourth check at all (--no-daemon).

Client(&'a ControlClient)

Run it against this daemon.

Unavailable(String)

There is no daemon to hand off to, and this is why.